Abstract

OBJECT Syrinx size and location within the spinal
cord may differ based on etiology or associated conditions of the brain
and spine. These differences have not been clearly defined. METHODS All
patients with a syrinx were identified from 14,118 patients undergoing
brain or cervical spine imaging at a single institution over an 11-year
interval. Syrinx width, length, and location in the spinal
cord were recorded. Patients were grouped according to associated brain
and spine conditions including Chiari malformation Type I (CM-I),
secondary CM (2°CM), Chiari malformation Type 0 (CM-0), tethered cord,
other closed dysraphism, and spinal tumors. Syringes not associated with any known brain or spinal
cord condition were considered idiopathic. Syrinx characteristics were
compared between groups. RESULTS A total of 271 patients with a syrinx
were identified. The most common associated condition was CM-I
(occurring in 117 patients [43.2%]), followed by spinal dysraphism
(20 [7.4%]), tumor (15 [5.5%]), and tethered cord (13 [4.8%]).
Eighty-three patients (30.6%) did not have any associated condition of
the brain or spinal
cord and their syringes were considered idiopathic. Syringes in
patients with CM-I were wide (7.8 ± 3.9 mm) compared with idiopathic
syringes (3.9 ± 1.0, p < 0.0001) and those associated with tethered
cord (4.2 ± 0.9, p < 0.01). When considering CM-I-associated and
idiopathic syringes, the authors found that CM-I-associated syringes
were more likely to have their cranial extent in the cervical spine
(88%), compared with idiopathic syringes (43%; p < 0.0001). The
combination of syrinx width greater than 5 mm and cranial extent in the
cervical spine had 99% specificity (95% CI 0.92-0.99) for
CM-I-associated syrinx. CONCLUSIONS Syrinx morphology differs according
to syrinx etiology. The combination of width greater than 5 mm and
cranial extent in the cervical spine is highly specific for
CM-I-associated syringes. This may have relevance when determining the
clinical significance of syringes in patients with low cerebellar tonsil
position.